IGNITION WILL NOT ENGAGE THE ENGINE IN MY TRUCK, WHAT COULD BE WRONG?

1989 Ford F-150 • 268,000 miles

I have a 1989 F150 6 cyl, manual tranny, I replaced the ignition switch on top of the steering column and the ignition assembly as well. I have recently replaced all solenoid, starter, and alternator. The actuator rod moves back and forth when I turn the key over so I know its not the actuator arm behind the steering wheel. What else could this be? I go to turn the key and I hear everything come on lights, radio, fuel pump etc, but when I go to turn it over the key just stays all the way over.